I just ate a pizza made out of hamburgers. By that I mean that I tried Burger King's new Pizza Burger, a 2,530-calorie monstrosity that includes four hamburger patties, pepperoni, mozzarella and something called Tuscan sauce on an enormous sesame-seed bun. The $13 megaburger is 9.5 in. (24 cm) in diameter  the size of a small pizza  and is the caloric equivalent of nearly four Whoppers. I made it through two slices before I called it quits. (Watch Claire Suddath and others eat mega-sandwiches and rank their flavors.)

The Pizza Burger may be the largest burger produced by a fast-food chain, but the foot-long (30 cm) cheeseburgers at Hardee's and Carl's Jr. aren't far behind. For a while, West Coast chain Red Robin stuffed burgers with mozzarella sticks. East Coast chain Friendly's sometimes wedges a patty between two grilled-cheese sandwiches. Oversize concept burgers are everywhere. "This is what everyone in the industry is doing now," says Brad Haley, vice president of marketing for CKE Restaurants, the parent company of Carl's Jr. and Hardee's. "We still offer low-fat, low-carb alternatives, but those never sell as well as big hamburgers do." (See the top 10 worst fast-food meals.)

America's century-long love affair with the hamburger has survived health trends, the processed-food backlash, even the recession. But the past decade has seen a shift in consumption patterns from the traditional patty-and-bun combination to what marketing executives call premium and specialty burgers that focus on high-quality beef and previously uncommon accoutrements. That helps explain why restaurants are touting gourmet toppings, creating novelty proportions and making buns out of everything from soft pretzels to glazed doughnuts.

Given that nearly 27% of U.S. adults are not just overweight but obese, the idea of a pizza-size sandwich might be cause for hand wringing and finger wagging, but very few Burger King customers will actually have access to it. Right now, the supersize item is available only at the BK Whopper Bar in New York City. "These extreme foods are oftentimes just a stunt, something to get the consumer to think about their restaurant," says Brian Wansink, director of Cornell University's Food and Brand Lab and author of Mindless Eating. "Take the KFC Double Down, for example. If no one had ordered it, would it have still been a good idea? Absolutely. It made them seem edgy."

On the consumption side, media stunts can get a restaurant only so far. Freakishly large burgers provide amusement, maybe earn the eater some bragging rights, but in the end they offer nothing more than a hint of pizza sauce or a slight doughnut aftertaste. The foot-longs don't even have that. After all, food can't taste longer.

This article originally appeared in the Oct. 11, 2010, issue of TIME magazine.